(1) Field of the Invention
The present invention relates to a packet communication node apparatus, and more particularly to a modular type node apparatus for packet communication capable of additionally accommodating extension modules each provided with a specific communication service function.
(2) Description of the Related Art
A packet communication node apparatus, such as a router or a packet switch, basically comprises a control module for updating a destination table (routing table) by executing a predetermined routing protocol, a plurality of network interface modules each for communicating packets with network lines, and a switching unit for mutually connecting these modules. Each network interface module adds internal routing information designated in the destination table to each of packets received from a network, and the switching unit forwards the packet received from each network interface module to one of the other modules in accordance with the internal routing information.
As the IP (Internet Protocol) network has come into extensive use and the communication service becomes more rapid and advanced, packet communication node apparatuses are required to have functions to provide specific communication services in addition to the packet exchanging function. Therefore, in order to promptly respond to requests from users (communication service operators), it will be effective for any manufacturer supplying packet communication node apparatuses to supply a modular type node apparatus for which, for instance, spare connection ports for connecting additional modules to the packet switching unit are kept available, so that when a user requests the addition of a specific service function, it can additionally accommodate in its packet switching unit an extension module designed to meet the user's requirements. In this case, the setting of control data, needed for operating the extension module, into the packet communication node apparatus would pose a problem.
In the field of information processing systems, as described in Japanese Patent Application Laid-Open No. 2000-132487 (Patent Reference 1) for instance, there is proposed a system in which driver software needed on the server side is built in advance into each of peripheral devices to be connected to a server via a network. When the server selects any of the peripheral devices to operate it, if the module (driver software) needed for the operation of this peripheral device is found absent on the server side, the server sends a message requesting the driver software to the peripheral device. The server stores the driver software received from the peripheral device and operates the peripheral device by executing the stored driver software.
The system proposed in Patent Reference 1 is characterized in that, when a new peripheral device is added to the server, the server noticing the absence of the driver software needed for operating the peripheral device, requests the peripheral device for transmitting the driver software. In this case, the peripheral device newly added to the system has no active part in sending the control information to the server. Therefore, if it is attempted to apply this configuration to the above-described packet communication node apparatus, the control module or each network interface will play the active part in acquiring control data from the newly added extension module. In the case of a packet communication node apparatus, however, each network interface only operates, every time a packet is received, so as to refer to a destination table prepared in advance, add internal routing information corresponding to the destination module address to the received packet and supply the packet to the switching unit. The network interface has no function to detect the absence of routing information for the extension module and to request the extension module for such control data. Nor can the control module detect the absence of control data for the extension module, because it is in no position to operate the extension module by using control data for the extension module.